Do women talk negative about men they are attracted to?
It depends on the personality of the girl. Some people are positive and some are negative. Some believe they should not talk about others so they avoid it while others gossip to bond or feel better about themselves.
If a girl is teasing with insults, that may be her flirtation style. If she is saying things about a guy behind his back she may be covering the fact that she likes him so others will not suspect. She could also be doing it to deter other women from being interested. Another motive could be she is fishing for advice on how to deal with that guy from other people, or hoping to hear what they think about it.
Bottom line, women can talk negatively about a guy they are attracted to. Why she might do it depends on her. There are women though that would not.